Mockowanie modułów i funkcji w TypeScript

const mockFn = jest.fn<number, [string]>();
mockFn('hello'); // typed call

jest.mock('./api');
import { fetchUser } from './api';
const mockFetch = fetchUser as jest.MockedFunction<typeof fetchUser>;

jest.mock('./api');
import { fetchUser } from './api';
const mockFetch = jest.mocked(fetchUser);
mockFetch.mockResolvedValue({ id: 1, name: 'Alice' });

mockFetch.mockResolvedValue({ id: 1, name: 'Alice' }); // must match User type

const spy = jest.spyOn(userService, 'findUser');
spy.mockResolvedValue(mockUser);

jest.mock('./db', () => ({
  findUser: jest.fn(),
  createUser: jest.fn(),
}));

const mockDb = jest.createMockFromModule<typeof import('./db')>('./db');

jest.mock('./email', () => ({ ...jest.requireActual('./email'), sendEmail: jest.fn() }));

afterEach(() => { jest.clearAllMocks(); });
// Or globally: jest.config clearMocks: true

const mockRepo: jest.Mocked<UserRepository> = {
  findById: jest.fn(),
  save: jest.fn(),
  delete: jest.fn(),
};